There can be many issues that can be causing this problem on your printer. I have encountered the same problem before with our Artisan 725 (which essentially the same printer) but the problem usually occurs when I attempt to scan a document of image. My issue could be the scanner bed.
I'm curious, when you print a nozzle check, are all the lines appearing on the print out?
Also check to if there's any air in the lines and check to physically see if the cartridges are full of ink as well.
If you can, e-mail an image of what you're describing to me so that I can know what you're talking about. firstname.lastname@example.org
If you wish, you can also give us a call (626) 575 0860.